1. Field of the Invention
The present invention generally relates to a power supply circuit and, in particular, to a protection circuit and a control method for a power supply capable of switching on and off.
2. Description of the Related Art
There has been widely used a fused circuit which concurrently does overcurrent detection and power supply interception for protection. For instance, a power supply circuit provided with a fuse for each power supply terminal and a fuse monitoring circuit has been disclosed in the Japanese Utility-model Unexamined Publication No. 2-124567. When the fuse opens, the fuse monitoring circuit notifies the computer of blowing the fuse.
Another power supply circuit has been disclosed in Japanese Patent Unexamined Publication No. 4-322314. This conventional power supply circuit is provided with an overcurrent detection circuit and a power supply interception circuit which are independently installed. When the overcurrent is detected, the power supply interception circuit automatically intercepts the power supply.
In the case of the fuse circuit, however, it is necessary to replace the burnt fuse with a new one so that the power supply may be returned. Therefore, the maintenance becomes complex. Moreover, the fuse monitoring circuit which connects the power supply line and the computer needs a buffer circuit for adjusting the voltage of the monitor signal output to the computer.
In the case of the power supply circuit which uses the overcurrent detection circuit and the power supply interception circuit, it is necessary to install an alert circuit for informing an operator of the power supply interception. Moreover, there is no description or suggestion about the return of power.